Structural changes in bacterial and fungal soil microbiome components during biosolarization as related to volatile fatty acid accumulation

Abstract Biosolarization is an integrated pest management strategy that combines soil solarization with organic amendment application. In the present study, soil samples were taken after biosolarization using tomato pomace and green waste compost (GWC) amendments and analyzed to elucidate changes to the soil microbiome, including both fungal and bacterial communities. Following a field trial wherein soil mesocosms were biosolarized for 8 days, the effects of soil depth and soil amendments were assessed via sequencing and bioinformatic analysis of 16S rRNA gene and ITS2 amplicons generated from soil microbial genomic DNA. Structural and network analyses were used to quantify differences in microbiota between treatments and these results were correlated with measured levels of volatile fatty acids in the soils. The results showed that biosolarization had a stronger impact on the bacterial community relative abundance profile than on the fungal community at the phylum and order levels. However, at the operational taxonomic units (OTUs) level, biosolarization treatment had a significant impact on both fungal and bacterial communities, across soil depth and GWC addition. Co-occurrence microbial network analysis revealed a unique circular network consisting of 8 discrete clusters. Correlation between the clusters and soil volatile fatty acid (VFA) production suggested that the bacterial Clostridium, Weissella and Acetobacter genera tolerate, and perhaps drive, VFA accumulation. Notable fungal community effects included significantly reduced relative abundance within genera known to contain plant pathogenic members, such as Gibberella, Haematonectria, Fusarium, Aspergillus and Alternaria.